This invention relates to oral products. More particularly, this invention relates to oral products capable of remineralizing subsurface dental lesions and mineralizing exposed dentinal tubules and having improved whitening and stain removal properties.
Remineralizing/mineralizing products have been developed to overcome the damage caused by dental caries, i.e., tooth decay, which is a leading cause of tooth damage in humans. Dental caries usually begins with lesions, which are demineralized areas below the surface of intact dental enamel. These lesions are sometimes visible as "white spots" on the surface of the enamel. If unchecked, enamel within and above a subsurface lesion eventually collapses, leading to cavitation and subsequent loss of tooth structure.
Oral products designed to remineralize subsurface lesions in teeth and mineralize exposed dentinal tubules, i.e., remineralizing/mineralizing products, are disclosed, for example, to U.S. Pat. No. 4,080,440 (DiGiulio et al.); U.S. Pat. Nos. 4,177,258, 4,183,915 and 4,348,381 (all to Gaffar et al.); U.S. Pat. No. 4,083,955 (Grabenstetter et al.); U.S. Pat. No. 4,397,837 (Raaf et al.); U.S. Pat. Nos. 4,606,912 and 4,610,873 (both to Rudy et al.); U.S. Pat. Nos. 5,037,639, 5,268,167, 5,437,857, 5,427,768 and 5,460,803 (all to Tung); U.S. Pat. No. 5,605,677 (Schumann et al.); U.S Pat. No. 5,603,922 (Winston et al.); U.S. Pat. No. 5,605,675 (Usen et al.); U.S. Pat No. 5,571,502 (Winston et al.); U.S. Pat. No. 5,614,175 (Winston et al.); and U.S. Pat. No. 5,645,853 (Winston et al.).
Remineralization can only occur when the tooth structure is still basically intact before a cavity is formed.
In the remineralizing/mineralizing oral products disclosed in the above-cited references, remineralization and mineralization are achieved by increasing the calcium and phosphate ion content in the oral cavity. This is because the primary component of the enamel and dentin in teeth is calcium phosphate in the form of calcium hydroxyapatite.
However, the addition of calcium and phosphate ions in an effective form by dentifrices is not a simple matter. Calcium ions are rather reactive with the conventional ingredients for these products, and can lose their effectiveness virtually entirely by being chemically combined with such ingredients. For example, calcium cannot just be added to dentifrices in the presence of phosphate ions because the two will react with each other to form an insoluble calcium phosphate, which is not effective. By the same token, calcium ions cannot just be combined with fluoride ions because of the precipitation of calcium fluoride, which is also ineffective.
Thus, in the oral products disclosed in the references cited above, premature reaction between the calcium, phosphate and fluoride salts is avoided by keeping the calcium salt physically separate from the phosphate and fluoride salts, by disposing either or both of the cationic and anionic parts in a non-aqueous medium, or by adding a stabilizing agent (e.g., chelating agent, antinucleation agent or water-soluble, non-calcium divalent metal salt) to the product.
Another dental concern for many people is the whiteness of their teeth. For a variety of reasons, it has become desirable for a person's teeth to appear bright or "white". Society places a high value on the "whiteness" of one's teeth. One whose teeth are white may enjoy more personal confidence and satisfaction and may even enjoy greater social acceptance.
A tooth is composed of an inner dentin layer and an outer hard enamel layer that is the protective layer of the tooth. The enamel layer of a tooth is naturally an opaque white or slightly off-white color. While the dentin below the enamel can sometimes be stained for systemic reasons, such as ingestion of tetracycline while teeth are forming, often it is the enamel layer that can become stained or discolored due to extrinsic deposits in the pellicle. Also, the enamel layer of a tooth is composed of hydroxyapatite mineral crystals that create a somewhat porous surface. As a result, the surface of the enamel layer presents microscopic spaces or pores. The porous nature of the enamel layer can allow staining agents and discoloring substances to permeate the enamel and discolor the tooth.
Many substances that a person confronts or comes in contact with on a daily basis can "stain" or reduce the "whiteness" of the teeth. In particular, colored residues from foods, tobacco products, and fluids that one consumes tend to accumulate in the pellicle layer over the teeth. These staining and discoloring substances can permeate the enamel layer. This problem usually occurs gradually between visits to the dentist, but imparts a noticeable discoloration of the enamel of the teeth. Often, surface stains are removed when the dentist performs a prophy. However, more aggressive treatment is sometimes required. As long as the discolored teeth are still healthy and do not pose any health risk or problem, a product or substance that would whiten the discolored teeth would be advantageous. Such a product would maintain the whiteness of teeth between visits to the dentist.
Oral products for whitening and/or removing stains from teeth are known in the art. Reference is made, for example, to U.S. Pat. No. 5,256,402 (Prencipe et al.), U.S. Pat. No. 5,713,738 (Yarborough), U.S. Pat. No. 5,401,495 (Murayama), U.S. Pat. No. 5,171,564 (Nathoo et al.), U.S. Pat. No. 5,041,280 (Smigel), U.S. Pat. No. 5,814,304 (Wong et al.), and U.S. Pat. No. 5,279,816 (Church et al.). Oral products which are said to reduce plaque and gingivitis with reduced staining are also known. Reference is made, for example, to U.S. Pat. Nos. 5,145,666 and 5,281,410 (both to Lukacovic et al.). Calculus-inhibiting compositions are disclosed, for example, in U.S. Pat. No. 4,289,753 (Dyroff et al.).
Many discoloring residues found on the teeth contain heavy metal ions such as iron, copper and manganese. For example, lipstick residues on the teeth contain iron ions. One way to improve whiteness and remove stains is to use a chelating agent for these metal ions. For example, U.S. Pat. No. 5,713,738 to Yarborough teaches that the use of sodium silicate as a thickener therein is beneficial because of its affinity for iron and other heavy metals. U.S. Pat. No. 5,256,402 to Prencipe et al. teaches the use of chelating agents to stabilize peroxide-containing compositions by chelating metal ions such as Fe.sup.+3, Mn.sup.+2 and Cu.sup.+2. Examples of these chelating agents include the salts of ethylene diamine tetraacetic acid, diethylene triamine pentaacetic acid, phosphonates such as Dequest.RTM. (available from Monsanto Chemical Company), and azacycloheptane 2', 2' diphosphonate. In its background section, U.S. Pat. No. 4,289,753 to Dyroff et al. states that French Pat. No. 2,108,827 (published May 26, 1972) teaches that the calcium ion-sequestering capability of sodium gluconate can be used to remove tartar from teeth. Other patents teaching the use of sodium gluconate as an additive (not as chelating agents for calcium ions or heavy metal ions) include, e.g., U.S. Pat. Nos. 4,568,540; 4,664,906; 4,814,163; 4,902,497; 4,992,259; 5,004,597; 5,145,666; 5,281,410; 5,281,411; and 5,338,537.
It would be desirable to provide a single oral product which is capable of remineralizing subsurface lesions in teeth and mineralizing exposed dentinal tubules and of whitening teeth. In particular, it would be desirable to provide a single oral product which is capable of remineralizing subsurface lesions in teeth and mineralizing exposed dentinal tubules and of whitening teeth, wherein whitening is achieved by means of a chelating agent for heavy metal ions. However, this is not a simple matter because of the reactivity of the calcium ions. In other words, the chelating agent which is used to improve whitening must chelate the heavy metal ions but not the calcium ions which are needed to effect remineralization and mineralization.
Thus, it is desirable to improve the whiteness properties of a remineralizing/mineralizing oral product without adversely affecting the remineralizing and mineralizing properties.
A primary object of this invention is to provide a single oral product having both remineralizing/mineralizing properties and whitening (stain-removal) properties.
A further object of this invention is to improve the whitening (stain-removal) properties of a remineralizing/mineralizing oral product without adversely affecting the remineralizing and mineralizing properties.
Another object of this invention is to provide a remineralizing/mineralizing oral product having improved whitening and stain-removing properties but which does not excessively abrade the teeth.
A further object of this invention is to provide an oral product having the aforementioned properties, wherein the product is easy to use by consumers and does not differ significantly in flavor and appearance from customary oral products.
These and other objects which are achieved according to the present invention can be readily discerned from the following description.